PDBsum entry 2q1v

Transcription

PDB id: 2q1v

Contents

Protein chain

244 a.a. *

Ligands

PDN

GOL

Waters ×181

* Residue conservation analysis

PDB id:

2q1v

Name:

Transcription

Title:

Ancestral corticoid receptor in complex with cortisol

Structure:

Anccr. Chain: a. Engineered: yes. Mutation: yes

Source:

Unidentified. Organism_taxid: 32644. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.95Å R-factor: 0.207 R-free: 0.233

Authors:

E.A.Ortlund,M.R.Redinbo

Key ref:

E.A.Ortlund et al. (2007). Crystal structure of an ancient protein: evolution by conformational epistasis. Science, 317, 1544-1548. PubMed id: 17702911 DOI: 10.1126/science.1142819

Date:

25-May-07 Release date: 04-Sep-07

Protein chain

No UniProt id for this chain

Struc: 244 a.a.

DOI no: 10.1126/science.1142819

Science 317:1544-1548 (2007)

PubMed id: 17702911

Crystal structure of an ancient protein: evolution by conformational epistasis.

E.A.Ortlund, J.T.Bridgham, M.R.Redinbo, J.W.Thornton.

ABSTRACT

The structural mechanisms by which proteins have evolved new functions are known only indirectly. We report x-ray crystal structures of a resurrected ancestral protein-the approximately 450 million-year-old precursor of vertebrate glucocorticoid (GR) and mineralocorticoid (MR) receptors. Using structural, phylogenetic, and functional analysis, we identify the specific set of historical mutations that recapitulate the evolution of GR's hormone specificity from an MR-like ancestor. These substitutions repositioned crucial residues to create new receptor-ligand and intraprotein contacts. Strong epistatic interactions occur because one substitution changes the conformational position of another site. "Permissive" mutations-substitutions of no immediate consequence, which stabilize specific elements of the protein and allow it to tolerate subsequent function-switching changes-played a major role in determining GR's evolutionary trajectory.

Selected figure(s)

Figure 2.
Fig. 2. Mechanism for switching AncGR1's ligand preference from aldosterone to cortisol. (A) Effect of substitutions S106P and L111Q on the resurrected AncGR1's response to hormones. Dashed lines indicate sensitivity to aldosterone (green), cortisol (purple), and DOC (orange) as the EC[50] for reporter gene activation. Green arrow shows probable pathway through a functional intermediate; red arrow, intermediate with radically reduced sensitivity to all hormones. (B) Structural change conferring new ligand specificity. Backbones of helices 6 and 7 from AncGR1 (green) and AncGR2 (yellow) in complex with cortisol are superimposed. Substitution S106P induces a kink in the interhelical loop of AncGR2, repositioning sites 106 and 111 (arrows). In this background, L111Q forms a new hydrogen bond with cortisol's unique C17-hydroxyl (dotted red line).

Figure 4.
Fig. 4. Structural identification of an ancient permissive substitution. (A) Comparison of the structures of AncCR (blue) and AncGR2 (yellow). Y27R generates a novel cation- interaction in AncGR2 (dotted cyan line), replacing the weaker ancestral hydrogen bond (dotted red) and imparting additional stability to helix 3. (B) Y27R is permissive for the substitutions that confer GR function. Reporter gene activation by AncGR1 + XYZ (upper right) is abolished when Y27R is reversed (lower right). (Left) Y27R has negligible effect in the AncCR background (or in AncGR1, fig. S9). Green, orange, and purple lines show aldosterone, DOC, and cortisol responses, respectively. Green arrows, likely pathway through functional intermediates.

The above figures are reprinted by permission from the AAAs: Science (2007, 317, 1544-1548) copyright 2007.

Figures were selected by an automated process.